Single carrier modulation, a commonly used method in high-speed underwater acoustic communications, requires equalization at the receiver. However, its performance remains suboptimal rapidly time-varying channels. Recently, delay-Doppler (DD) domain such as well-known orthogonal time frequency space (OTFS) has garnered considerable attention for ability to provide more reliable communication highly dynamic environments. OTFS is essentially precoded division multiplexing (OFDM) that...

This paper investigates energy allocation in underwater acoustic nodes powered by harvesting. Our goal is to maximize the expected total amount of delivered data over a finite time slots. Two scenarios are considered for different knowledge levels channel state information (CSI). In one scenario, transmitter receives CSI at end each transmission epoch and we consider problem sensing transmission. second delayed after multiple slots, while only considered. The modeled as finite-state Markov...

Underwater acoustic channels, influenced by time-varying, space-varying, frequency-varying, and multipath effects, pose significant interference challenges to underwater communication (UWAC) signals, especially in non-cooperative scenarios. The task of modulating identifying distorted signals faces huge challenges. Although traditional modulation recognition methods can be useful the radio field, they often prove inadequate environments. This paper introduces a system for recognizing UWAC...

This paper addresses sparse channels estimation problem for the generalized linear models (GLM) in orthogonal time frequency space (OTFS) underwater acoustic (UWA) system. OTFS works delay-Doppler domain, where time-varying are characterized as impulse responses. In fact, a typical doubly spread UWA channel is associated with several resolvable paths, which exhibits structured sparsity domain. To leverage of channel, we develop sparsity-based approximated message passing (GAMP) algorithm...

A key research area in underwater acoustic (UWA) communication is the development of advanced modulation and detection schemes for improved performance range-rate product. In this communication, we propose a variable-rate data transmission system based on direct sequence spread spectrum (DSSS) complementary code keying (CCK), particularly shallow-water channels with severe multipath propagation. We provide suboptimum receiver that consists bidirectional decision feedback equalizer (BiDFE) to...

Aimed at solving the problem of low data rate direct sequence spread spectrum underwater acoustic communication and that complexity receivers M-ary communication, cyclic shift keying is proposed based on good characteristic sequences. At transmitter, base waveform cyclically shifted according to input information. receiver, only one correlator used estimate time delay decode. Multi-code presented. Lake experiments both middle long range were conducted for methods. Single two code realized in...

Single carrier modulation with frequency domain equalizer is proposed for underwater acoustic channel. An unique training sequence, viewed as cyclic prefix, inserted into transmitted sequences so that low complexity minimum mean square error (MMSE) equalization (FDE) used combating the inter-symbol interference in receivers. Maximum likelihood estimation robust initial phase and Doppler shift are derived by using sequence. The receiver estimates error, channel block-by-block. Compare to zero...

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Recently, single carrier block transmission (SCBT) has received much attention in high-rate phase-coherent underwater acoustic communication. However, minimum-mean-square-error (MMSE) linear FDE may suffer performance loss the severely time dispersive channel. To combat channel distortion, a novel multi-channel receiver with maximum ratio combining and low complex T/4 fractional iterative frequency domain equalization (FDE) is investigated to improve diversity gain bit error rate (BER)...

Abstract The increasing demand for exploring and managing the vast marine resources of planet has underscored importance research on advanced underwater acoustic communication (UAC) technologies. However, owing to severe characteristics oceanic environment, (UWA) propagation experiences nearly harshest wireless channels in nature. This article resorts perspective machine learning (ML) cope with major challenges adaptive modulation coding (AMC) design UACs. First, we present an ML AMC...

Acoustic communication between fast-moving underwater vehicles is difficult due to the fact ratio of vehicle speed sound many times exceeds its counterpart in mobile radio channels. Hence, symbol synchronization, as important carrier frequency identification, critical for wireless communication. In this paper, we propose a reliable using wideband chirp signals and novel self-synchronization method. The use takes advantage low Doppler sensitivity well their good autocorrelation properties....

Single-carrier with frequency domain equalization (SC-FDE) has been considered for bandwidth efficiency underwater acoustic (UWA) communication recently due to its reduced computational complexity and low peak-to-average power ratio. A multi-channel time-frequency method pseudurandom noise (PN) based SC-FDE is proposed in this paper. The equalizer includes a followed by order adaptive time decision feedback (DFE). algorithm applied the real data receiving from lake test conducted November...

Orthogonal time-frequency-space (OTFS) modulation has shown significant error performance advantages over orthogonal frequency division multiplexing (OFDM) in time-varying channels. However, the symbols OTFS frames still suffer from inter-Doppler interference (IDI) and inter-symbol (ISI). In this letter, we propose a two dimensional (2D) adaptive multichannel decision feedback equalizer (DFE) to combat interference. The proposed receiver constructs input signal of DFE based on characteristic...

With the development of underwater acoustic (UWA) adaptive communication system, energy-efficient transmission has become a critical topic in communications. Due to unique characteristics environment, transmitter node will almost always have outdated channel state information (CSI), which results low energy efficiency. In this paper, we take full advantage bidirectional links and propose an modulation coding (AMC) scheme that aims maximize long-term efficiency single link by jointly...

An improved direct adaptive multi-channel turbo equalization receiver structure employing Doppler compensation is proposed for wireless communications over sparse underwater acoustic (UWA) channels. Compared to existing schemes that have been used communications, two novel techniques are employed improve the overall system performance: 1) extrinsic log likelihood ratio (LLR) output by equalizer, and exchanged between equalizer decoder calculated taking into account a prior probability of...

Single-carrier frequency-domain equalization (SC-FDE) is a promising technique for coherent high-rate underwater acoustic (UWA) communications. In this paper, time-frequency domain turbo (TFD-TE) scheme proposed single-carrier modulation. The TFD-TE to couple multi-channel frequency equalizer with phase rotation compensation and low-order single-channel time-domain equalizer. To mitigate the error propagation further enhance receiver performance, bidirectional that combined soft outputs of...

This work proposes a novel interleave-division multiple access (IDMA) system based on cyclic shift keying (CSK) modulation, named CSK-IDMA, for multiuser underwater acoustic (UWA) communications. The CSK modulation uses circular of the spreading sequence to represent information, which can be viewed as special M-ary spread spectrum modulation. Compared with conventional direct-sequence (DSSS) technique, overcomes gain versus data rate limitations. proposed scheme adopts IDMA technique reduce...

This study proposes a novel approach to joint channel estimation and detection of orthogonal frequency division multiplexing transmission over underwater acoustic (UWA) multipath channels exhibiting cluster sparsity. Unlike most sparse estimations, the authors exploit cluster‐sparsity characteristic UWA without additional prior information. They adopt modified spike‐and‐slab model in their non‐parametric Bayesian learning framework. To avoid need for closed‐form estimate, they apply Markov...